Electrochemical energy conversion and storage in new, advanced battery systems will undoubtedly contribute to finding solutions to the world's energy problems and, in particular, to lessening its dependence on fossil fuels for transportation. Non-aqueous, lithium batteries offer the most flexible chemistries and the best promise for greater-than-incremental improvement over known battery systems, particularly in terms of their practical energy and power performance.
The most significant advantage of non-aqueous lithium batteries over aqueous systems is that they can operate at voltages significantly higher than the decomposition potential of water (about 1.2 V). Despite the progress that has been made in recent years with conventional lithium-ion cells, such as those that use lithiated graphite (LixC6) or lithium titanate spinel Li4Ti5O12 negative electrodes (anodes) in combination with lithium-metal-oxide or lithium-metal-phosphate positive electrodes (cathodes), for example, layered LiCoO2, LiNi0.8CO0.15Al0.05O2 and LiNi0.33Mn0.33Co0.33O2, spinel LiMn2O4, olivine LiFePO4 or compositional modifications thereof, the energy and power densities of rechargeable lithium-ion batteries, notably for applications such as electric vehicles and plug-in hybrid electric vehicles, are still limited by the specific and volumetric capacities of the electrode materials currently in use. New materials and cell designs are required to advance lithium battery technology. Lithium-oxygen (or lithium-air) cells offer the possibility of significantly increasing the energy density and performance of lithium-based electrochemical power systems. Because oxygen is supplied as a fuel to the cathode during discharge, a lithium-oxygen (air) cell can be considered to be a battery/fuel cell hybrid. However, the practical implementation of such cells is hampered, largely by the complexity and limitations of the oxygen (air) electrode. The present invention provides novel electrocatalyst materials for the positive electrode (cathode) for a future generation of lithium-oxygen (air) electrochemical cells and batteries. The invention also provides examples of such electrocatalyst/electrode materials and methods for synthesizing the electrocatalysts/electrodes.